1. Field of the Invention
The present invention relates generally to a method for terminating an attach procedure in a mobile terminal of a mobile communication system, and in particular, to a method for terminating an attach procedure performed in a call process between a terminal and a network in response to the occurrence of an abnormal abort situation in a mobile terminal of a General Packet Radio Service (GPRS) mobile communication system.
2. Description of the Related Art
Currently, the use of a mobile terminal has been expanded to include a data service as well as a voice call. According to this, a General Packet Radio Service (GPRS) that enables data communication in an existing Global System for Mobile (GSM) communication system has been developed, and a Universal Mobile Telecommunication System (UMTS), one of 3rd generation communication systems, also has been developed to satisfy the requirements of more data and higher data rate.
To use such a data service, a mobile terminal performs an attach procedure and a packet data protocol (PDP) context activation procedure. The attach procedure and the PDP context activation procedure are performed by separate GPRS Mobility Management (GMM) and Session Management (SM), respectively. Thus, the PDP context activation procedure is performed in an SM layer to perform the data service, and to activate a PDP context, a GPRS service should be registered in a network through a GPRS attach procedure.
When the mobile terminal performs the GPRS attach procedure in a power-on state, only the PDP context activation procedure is performed for the data service. Otherwise, for the data service, the GPRS attach procedure is performed and then the PDP context activation procedure is performed. Herein, according to implementation methods, the attach procedure can be performed when the mobile terminal is turned on or when a user wants to use the data service. If the attach procedure is performed when the mobile terminal is turned on, a call setup time can be reduced by immediately performing the PDP context activation procedure when the user requests the data service, and packet switched (PS) paging can be served.
However, besides the fact that periodic routing area updating is performed, normal routing area updating should be performed every time when a routing area is changed, and as a result the mobile terminal consumes more power. In addition, when routing area updating is performed while the user is not using the data service, if a rejection is received due to a temporarily bad network state, a bad impression can be given to the user. On the contrary, if the attach procedure is performed only when the user uses the data service, advantages and disadvantages opposite to the above description exist.
Presently, unlike the voice call, paging is hardly used for the data service. In addition, since a mobile originated (MO) PS call by which a user initiates a service is mainly used and no application using a mobile terminated (MT) PS call exists, the two methods described above can be used.
As described above, in the prior art, when an attach procedure is performed only when a user uses a data service, if the user attempts the data service and cancels the data service before a PDP context activation procedure is completed, the PDP context activation procedure is aborted in an SM layer but the attach procedure performed in a GMM layer is not aborted. In addition, if the GPRS attach procedure has been already completed, a detach procedure is not performed.
In another case, when the user attempts the data service, if an attach accept message from a network in response to an attach request message from a mobile terminal does not exist due to a bad network state or a bad wireless environment, the user will typically cancel the data service without waiting for an extended time period for the response. However, though the data service has been cancelled by the user, a GPRS attach procedure attempted by the data service is continuously attempted with reference to a timer and an attempt counter defined by a protocol, and thus, the GPRS attach procedure is completed only when the mobile terminal enters into a stable network.
As described above, since a case where a GPRS attach procedure is performed when a user uses a data service cannot be discriminated from a case where the GPRS attach procedure is performed when a mobile terminal is turned on, an unnecessary attach procedure is performed in the situation described above.